Have finally started on the Clarkson Tandem engine build as per the Blackgates castings, which I had purchased some two years ago from Jo.

The kit was incomplete but I have ordered the missing castings, where appropriate, and will collect them at the Midlands Exhibition in two weeks time, and I am planning on building it as a tandem with 2 LP cylinders and not a tandem compound with HP and LP cylinders.

However, to get things rolling I have started on the build and it seemed that the first action should be to keep Jo happy, so I decided that the cylinder block assembly with steam chest and cover should be held together with studs and nuts, and I trust that she approves.

The next series of interconnected parts are the crank discs, con-rods, crank pins and axle, and these are all from stock as per the drawings.

I have started on the cylinder blocks and got them down to within 25thou of the finished size, all nice and square and just waiting for the steam chest to be able to confirm the cylinder bore centre.

Hopefully work will progress at a faster rate once I have the remaining castings though already have some questions regarding the main bearings and bearing caps as from the drawings the castings seem to be extremely tight in machinable material.

Just one point a "tandem" engine is one that has the two cylinders in line with each other ( think tandem cycle), what you have there if it was built as a compound would be a "cross compound" or with the steam going straight into both cylinders will be a "twin" or double high" as the steam will be classed as high pressure from the boiler rather than low (expanded) steam from a HP cylinder.

I think I would be tempted to add some bronze bearings rather than run straight in the cast iron which would allow you to put the bearing in at whatever height you wanted if the base casting was too low, you have double the amount of bearing caps so can split them off ctr if required.

I'd also go for a 2 bearing crank not 4 and swap the baseplates over putting the flywheel into the inside of the "L" shaped base castings but that is probably a bit further than you want to go ;)

I tried reversing the baseplate castings on my 3D CAD assembly as you suggested, but it does not work out very well in practice.I think on mine I will remove the existing bearing lugs from the castings and make up some new ones to form a single bearing either side.

I'd only traced it off the drawing quickly to see if it would work, i seem to recall that one of the pads for the cylinder would need building out to help line things up . New bearing supports would make it easier and you could beef them up a bit which would look more appropriate maybe 4 studs per cap.

If I do one then it won't be a problem as I doubt I will use castings, maybe just a couple of 4" flywheels. I'll draw something up at some time maybe twin 24mm bores to go with my other engines or 18/30 compound that could be plumbed either way so you can run as a compound on steam and double high on air.

Back to the main bearings I notice there is a bit of an anomaly in the drawings (Clarkson Drawings).

The cylinder casting ctr height is shown as 1 1/16" and this sits on a pad that is cast into the top of the bed casting so lets say the pad stands proud by 1/16" after machining. This gives the engines ctr line at 1 1/8" above the top of the base casting.

The ctr of the main bearing is shown as 1 1 /16" above the top of the bed casting and it has no pad being part of the bed casting.

This gives an error of 1/16" which could be sorted in a number of ways depending where the casting has more metal than needed or where it may seem a bit tight but the extra 1/16" may help matters. Without a set of castings in my hand it's hard to say, maybe as they have been fondled a lot by Jo's hands she could shed some light on this unless it was one of the reasons she parted with them ;)

Thank you for the input and you are correct in that it is not a tandem I shall be attempting to build but a twin so will have compressed air entering both cylinders simultaneously, and hopefully timing will not be too much of an issue for balancing for smooth running.

The drawings as supplied are rather sketchy and leave a lot of analysing for final numbers so your comments about the crank height are very valid, and an earlier build log on here, from Canada, actually went your route with bronze caps mounted on undercut pedestals allowing for the crank to run totally in them rather than have a cast iron, gunmetal interface for bearing surface.

However, to get things rolling I have started on the build and it seemed that the first action should be to keep Jo happy, so I decided that the cylinder block assembly with steam chest and cover should be held together with studs and nuts, and I trust that she approves.

:ThumbsUp:

As for the crank height there is no drawing for the base plate other a sketch showing the height of the bearings and that should be the height from the bottom of the cylinder not to the unmachined surface of the base plates.

I think I mentioned to you Mike I still don't like the original Clarkson crosshead guides Erics ones were rather thin and very hard when we tried tickling them with a file :disappointed:

Jo

P.S. Please don't mention anything about me selling castings to you the sale pre-dates Surus' arrival and you know what he is like about protecting his castings ::)

Just for reference here are a couple of pictures from my Solidworks 3D assembly of this engine so far, it can be seen in the second image that there is very little material to play with around the main bearing pedestals and the crankshaft actually stands proud of them.

I will be making various detail changes to the design, but I am just modelling up in CAD what I have to start with from the existing castings and drawings.Ignore the con rods, they are just temporary dummies to simulate getting the engine to turn over for checking valve events etc.Phil

Phil, after a quick look at your CAD model the height of the engines ctr line looks like it could be dropped quite easily in two stages.

1. Machine 50% of the pad that the cylinder sits on away looks like about 1/16" could be gained that way.

2. There looks to a plenty of metal on the bottom of the cylinder castings that is not doing anything so material could be removed from here to lower the cylinder until it lines up with the height of the cleaned up bearing pedestals.

For those with these castings can I ask if any of you have drawings from Blackgates? I was wondering if they now just supply copies of the old Clarkson drawing which is what I have or if they have updated the drawings and possibly corrected these issues?

When I spoke to them previously they said that they were waiting to put some onto the market until they had got them built up to check things, I was hoping that these checks may have thrown up any problems. Even if a new drawing was not produced they could have noted it on the copy or simply enclosed an A4 sheet with notes on.

Maybe I'll have another word with them and see if they would be OK with me writing up a build from their castings for ME and I would include a set of upto date drawings, most likely in metric as the majority of beginners who may want these kits will be metrically minded.

If they are in the business of selling castings then one would think a decent set of drawings would boost sales which must be good business sense, selling the castings with the old poor drawings will tend to put people off not encourage them to buy. Its a shame that when they aquired the rights they also seem to have also gained the Clarkson reputation for undersize and chilled castings as part of the package :(

Unfortunately hemmingway's engines are not really suitable for a beginner and it is these beginners that would most benefit from correct drawings ::)

Really appreciate the 3D images you have posted and they explain a lot of the design.

Hi Jason,

Your suggestions regarding reducing the height of the cylinder blocks to fit in with the available pedestal heights has a lot of merit and one will I shall investigate much further as a possible option, instead of going the rote of cutting down the pedestal height dramatically and making two new crank bearing blocks from scratch.

Shhhh, and not only did I manage to get Jo to release this casting set but I also coerced her into parting with her Stothert and Pitt Beam engine castings :hellno:, and those are superb with individual A4 sheet drawings for each individual component.

Mike, that does seem to be the simplest way to get the height issue sorted out. Probably flatten the bottoms of the bed castings so you have a decent surface to put on the mill table then clean up the tops of the bearing pedestals until you have a good clean surface then do the cylinder pad and note what the height difference is once you get down to 0.040" - 0.062" above the bed. You can then use this dimension as the cylinder bore to base rather than the 1 1 /16" shown.

I also see that the Piston will hit the two cylinder covers as there is no allowance for an end space :wallbang: I suggest you make the piston 3/8" thick rather than the 7/16" shown which will leave 1/32" between it and the spigots on the cylinder covers.

It is a pity to hear that your trunk guides may be chilled as they are the most fiddly to fabricate if the bead detail around the slot is to be retained. Keep me posted on what they are like and I'll see if I can come up with a way forward if they are not usable as they are. You might want to try heating first. It would also be nice to loose the notches at the ends of the trunk guides which look to be a bit of an afterthought when it was found that the conrods hit the guide :facepalm:

If they are in the business of selling castings then one would think a decent set of drawings would boost sales which must be good business sense, selling the castings with the old poor drawings will tend to put people off not encourage them to buy. Its a shame that when they aquired the rights they also seem to have also gained the Clarkson reputation for undersize and chilled castings as part of the package :(

Unfortunately hemmingway's engines are not really suitable for a beginner and it is these beginners that would most benefit from correct drawings ::)

I am not so negative as you are JB about the excellent service that Blackgates provide :ShakeHead: How many Casting sets have you actually purchased from Blackgates? The castings Mike has are original Clarkson ones. I do not know how far Phil has got sorting through all the Clarkson stuff they acquired - they do have a business to run as well. Blackgates castings are normally good quality and very competitively priced, and they replace castings that are found to have problems, even years later :)

Kirt at Hemmingway's has lots of engines that are not up on his website as he is "still drawing them up" or waiting to be able to get the rights to draw them up. Some are basic other are much more interesting to build, the problem is I doubt that many more engine sets will see light of day :(

Mike :-X Surus is getting suspicious he is been busy doing an inventory of all his casting sets making sure none are missing and to think Colin is hoping to re-home a set of Sanderson Beam Engine castings from me at the Midlands show :paranoia:

I am not so negative as you are JB about the excellent service that Blackgates provide :ShakeHead: How many Casting sets have you actually purchased from Blackgates?

This is why I asked if people were working from Old Clarkson or new Blackgates castings/Drawings. You said they were in the business of selling castings and NOT managing the designs so I assumed from that statement that they were just selling the old drawings. It would still be nice to know from anyone with Blackgates supplied castings and drawings if any alterations have been made to the patterns so they better reflect what is on the drawings and/or the drawings have been ammended.

. You say they will replace old castings does that Mean Mike can get his chilled trunkguides replaced and what about the undersize bed castings? However if their castings are coming out undersize then unless they do some work to the patterns a replacement will be no better so not much point in asking for a replacement, better to work out a way to rework things or bin it and make from scratch

Well at least 75% of the Minnie came from them and I did top up a few Superba bits so that must be equal to several small stationary engine casting sets. :)

You say they will replace old castings does that Mean Mike can get his chilled trunkguides replaced and what about the undersize bed castings?

Mike does not have Trunk guide castings they are some of the castings missing from the set. Earlier I mentioned that here is no Clarkson bed casting drawing just a sketch of the bearing pedestal so it is difficult to see how you could show it is undersized.

I think asking a third party company to replace something that someone else made decades earlier is more than a bit cheeky :stickpoke:

Ah yes they were Eric's Guides, just thought they came from Eric to you and then to Mike

Well if the other dimensioned parts don't fit the bed must either be undersize or even more dimensions wrong on the drawing. The pad for the cylinder is also smaller than the cylinder :'(

Mike further to the note about the piston hitting the covers, also make the 2" rod distance 2 1/32" when you reduce the piston to 3/8" if you stick with the 2" there is barely enough length in the rod to stop it hitting the packing nut too ::)

Bridport will exchange old Stuart supplied castings, though I suppose they bought the company name and goodwill not just rights to the castings and drawings

I don't have any problems with the castings I purchased from Jo nor any problems with Blackgates, who are very proactive, and have ordered some of the missing castings, including the trunk guides, and am sure that if they are chilled then they will take some form of remedial action.

I am actually collecting the castings from their stand at the Midlands show in two weeks today.

Just as an aside, if they are chilled how high a temperature do I need to "thaw" them out and for how long, assuming that an ordinary domestic oven would be OK to use.

The only negative comments I would make about this particular engine is that the drawings, which comprise of two A3 sheets with a general arrangement drawing and a very bad engineering details drawing plus an A4 sheet listing the castings and their part number, and these are all the original H. Clarkson & Son issued 12th July 1968, and I suspect the castings are of a similar vintage.

I also have two Stuart kits, the 10H and 10V and the castings are either just on size or undersize and they were the old ones from the Channel Islands, though I am soldiering on with those.

Mike did your drawings come from Blackgates? if not may be worth asking them at the show if the ones they now supply have had any revisions and buy a set if they have.

You will need a bit more than your oven. The castings need to get to a good bright red and for something that size held there for at least 1/2hr before being allowed to cool very slowly. You can use a propane torch or if you have an open fire or wood burning stove put it in there for the evening and allow to cool overnight in the ashes. Sometimes it works better than others but worth a try on castings that are hard to come by.

The drawings came with the castings and I strongly believe that they are the original supply from Clarkson and not Blackgates.

I shall ask them about the drawings which they now supply and the drawings are available as a set of 2 for £7 but I expect that is an old price.

Interestingly, their web page covering Clarkson kits quotes "the drawings are lacking in detail and it is expected that the builder would embellish the design according to his requirements" so I do not believe that they have any new drawings available though I will enquire.

Thank you for the information regarding the heat requirements in the event of chill spots.

Phil was kind enough to share some of his CAD parts and I've had a little play with them. The two bearing version should not be too difficult to do.

Mostly moving the cylinder pad on the baseplate and cutting off one pedestal, I would probably also remove some width from the inside edge of the "L"

Also rounding the bottom of the cylinder casting so it sits on the bed plate and not hanging off the side.

A few more detailed tweaks will see the two engine halves a bit closer together but the basic concept seems to be possible. If the two bed castings were replaced with something else a very nice engine could start to emerge :)

If the two bed castings were replaced with something else a very nice engine could start to emerge :)

I was beginning to come to the same conclusion myself, if there needs to be so much modification to two seperate bedplates, why not chuck em in the bin and fabricate one bedplate that does the job properly and looks more in keeping with the general design. It would be much easier to keep the main bearings lined up if they were on one solid baseplate as well.

I keep looking at those trunk guides as well, that slot to clear the con rod looks to be an afterthought to me, maybe it fouled on the original prototype and that was the easy way out. To my eye it just does not look right though and I think I would have to do something about it if I ever get round to building it.

The idea started on ME where 4 bearings was being questioned so the "argument" was about that, I just said it would not take much for anyone with a set to convert to 2 bearings. What is in those couple of photos is the minimum amount of work that even a relative beginner could carry out.But as you say if you are going to pay £250 for the set and then throw some away it will be cheaper to start from scratch which you could probably do for £100-125.

Phil, a new base would allow the length to be stretched a bit so the conrod did not reach such a steep angle, turned rather than flat would also gain a bit of clearance and so the list goes on and before you know it you will have a mini Agnes sitting infront of you :LittleDevil:

Anyway must go now as someone sent me some more equipment to try out and I get to keep it :pinkelephant:

The idea started on ME where 4 bearings was being questioned so the "argument" was about that, I just said it would not take much for anyone with a set to convert to 2 bearings. What is in those couple of photos is the minimum amount of work that even a relative beginner could carry out.But as you say if you are going to pay £250 for the set and then throw some away it will be cheaper to start from scratch which you could probably do for £100-125.

Anyway must go now as someone sent me some more equipment to try out and I get to keep it :pinkelephant:

Mike didn't pay anything like that for his castings :lolb:

I hope it is a CNC Milling machine :ThumbsUp: I seem to recall Ketan had a spare one of those kicking around... I have lots of space so I would happily have given it a home instead I will have to settle for my new toy when it turns up next week :naughty:

I was going by the current price list, expect the missing ones he paid pro rate the current price for.

Not a CNC I turned that down when it was offered to me a couple of years ago though could be tempted now. He seems to be spending all his time playing with tehnew SX3.5 DZP if the number of videos he keeps sending are anything to go by, has quite an impressive cut and certainly shifts metal when run at 5000rpm. Hoping he may offer me that as it has got bright red handwheels :P

You are providing lots of food for thought with the redesigns, some of which are significant and in keeping with the concept of the castings and some which are a bit more dramatic, such as going with a two pedestal bearing support system rather than the four, which I shall stay away from.

For the conrod bearings I have stayed with the design but added an oil cup at the top of each con-rod and this will keep things nice and smooth and I shall not be running the engine for any significant length of time and only on compressed air, so don't think that will be an issue.

I do like the suggestion of increasing the tapers from the original 5/16" thick end down to 3/16" at the thin end to 1/4" thick to 3/16" thin and may well do so as having made the con-rods already it is not a difficult task to set them up again and do some more milling on the profiles.

I shall make a final decision once I have received the trunk guides, and hopefully machined them to the correct sizes and then check whether I have a striking conflict at the thin end and agree that the slots are an afterthought and do not look quite right.

I am currently working on the con-rod, valve rod and slide valve family and will post pics once completed, which should be in the next day or so, depending on the weather.

Yes it should not be too hard to add the taper to yours, should come out something like this though I have shown the big end hole 1/16" larger for a bearing.

One thing that would be worth thinking of on your trunk guides is taking a small cut where the nuts will bear on so that they are all sitting on a flat surface. It looks like the flange is thick enough so you could take 1/32" off and still keep to the drawings 1/8" flange thickness. The length of the trunk guide is missing off the drawing though the dimension line is there, if you make this 2.406" that should clear the conrod.

If you also fancied plunging into the top of the trunk guide just enough to form a 1/4" dia recess then a small disc could be JBWelded in and when set use a BS0 ctr drill to form an oil point. You could even make the disc a bit thicker and thread it for a small brass oil cup but just depends on how far you want to go.

Finally coat in bright red paint and you should have a much more attractive trunk guide than the original but still making use of the casting.

Hello allbeen a lurker for a bit and now I may be able to helpI have the drawings for the single cylinder mill engine which I think is one half of this one. I acquired the drawings from blackgates about 12 months ago and they are photocopys of the clarksons ones.the trunk guide has a dimension of 2 7/16".hope this helpsregardsPaul

Interesting information as my original drawings do not show any dimension for the length of the trunk guide and Jason has suggested a length of 2 13/32" and now your numbers are throwing up 2 7/16", which is only 1/32" out so within operational limits I think.

Safely back from the Midlands Model Engineering show and am now in a position to start organising the work plan for the machining of the castings and build the Clarkson engine, and am attaching a couple of pictures of the new castings from Blackgates and the now complete collection.

I have indeed been quiet of late, but have also been rather busy with my new vertical mill and generally cleaning up and re-organising my workshop, but have found plenty of time to generate swarf from the castings received from Blackgates, complete with hard spots.

This first post will show the progress on the steam chest and covers and the chest castings were undersize so I had to make some accommodation for the shortfall in their height as well as some changes to the inner dimensions of the chests as well.

I am not sure that my process flow or holding was the best but all seemed to go OK though I still have to drill and tap for the exhaust systems as well as the inlets, which will be of the quick release plastic push fit tubing type with flow controllers built in.

The next posts will contain updates regarding the next steps in the build process.

In continuation the next parts for manufacturing were the cylinders and the crank assembly for the valve drive system and the castings for the cylinders had a few hard spots but also had a generous overage in all dimensions, which proved to be very handy.

Trying to work out the correct flow for machining took quite a long time and also workpiece holding was an issue when turning so I had to resort to packing pieces to ensure a good spread of tension as well as security.

I didn't wait for the cast iron to vie delivered from Blackgates so used some cold rolled steel bar I had to turn down to size for the crank discs and rods and associated pins, and I do try to use collects as much as possible by turning down to the largest 5C colletI have, which is just over 1 1/8" mange to do all the turning quite easily by holding the turned spigot.

The next steps were to turn to size the end covers and gland nuts for the rear covers.

The castings were rather rough so I had to generate a reference dimension, turn down to a size and then based on that spigot do the rest of the turning and drilling. I suspect that this may not be the best way to operate but for me it seemed to work out OK.

The only deviation from the plans was that the bore is listed at being 1" which leaves no clearance for eh air borings so I reduced to bore down to 15/16" and made the locating spigots on all four covers to match.

The pistons are not turned yet so I will have to make sure that I get a nice sliding fit when those are being processed.

To ensure concentricity between the covers and the threaded holes in the cylinder I used a rotary table for the covers and then used the co-ordinate method for the cylinder and took turns at one hole at a time for drilling and tapping, and can confirm that all went rather well and seems to fit very well.

One last picture of the front end covers bolted to the cylinder and also am attaching a couple of pictures of the base plates, the condition of which may mean that I just make a common baseplate and manufacture different bearing pedestals which should overcome the height issue already discussed with you.

The next post will be related to the trunk guide and I shall be asking for assistance in how to proceed.

The attached pictures are all based on the trunk guides received and they are indeed very rough and have a few hard spots, though my problem is where do I start to obtain a datum point.

Initially I have placed one guide into the four jaw chuck and tried to centre it on the base, which assumes that that trunk is central to the base, and this is not 100% certain, or should I try to centralise the guide somehow and then turn the base on that datum.

The issue if how I clean up the trunk and still maintain the oval ridge which is the boundary for the guide relief opening and then bore the length of the guide to 5/8" whilst trying to hold an uneven surface.

Any suggestions are most welcome and if I was making this part from stock then it would not be a problem, well a slightly lesser problem.

How much spare diameter is there on the part that goes against the cylinder? It might be worth a quick skim on that face but only the face not the outside so it can go flat against the chuck face in a second.

The hardest part to get true is the end of the guide and that is where any miss alignment will look worse so I would centre up on that for turning then mount it on an arbour to do the cylinder end :)

I think I would hold it much as you have it but with a little more sticking out and some packers on the two sides so that the jaws are not inclinded to find the low spot in the opening.

It is unlikely that the outside of the trunk is round so when setting up in the 4 jaw get it central on the two sides and then central on the top/bottom. The face of the jaws will line it up along the lathes axis.

You can now face and bore all at the same setting which will ensure the bore is at right angles to the bolting face. If there is enough metal while still held like this you can tidy up the outside of the flange. There is also the option to skim the outer face of the flange so your nuts have a flat surface to seat on, alternatively the holes could be spot faced which would be my personal choice.

If the end of the bore does look a bit off when you take it out of the chuck that can just be fettled down until it is pleasing to the eye.

Good progress with the rest of the bits, you should have it running by Christmas at this rate.

The Clarkson build continues and with Jason's guidance and help I have now cleaned up and bored the trunk guides to size and the 5/8" bore provides a very good concentric key for locating the rear covers when I go to drill for the mounting holes.

My smallest boring bar, with sufficient length to bore the full depth meant that I had to drill out to 13mm before I could start boring, so various sized drills were used with a focus on maintaining a true horizontal axis through the guide.

The remaining work on the trunk guides is to align them vertically relative to the ribs and bore out the 5/16" slots on both sides and also to drill and tap for an oil cup on each guide.

The last two pictures show both guides finished apart from the horizontal slots and 8BA mounting holes and these operations will be completed in the next couple of days.

Hopefully the next steps will be the eccentric and eccentric straps and con-rod, though in this case the castings are quite generous in oversize and of apparently good quality in gunmetal and cast iron.

Did not think that far ahead and was thinking that I could tighten the gland whilst the guide was disconnected and then couple the crank rod to the crosshead via the slot, as the access via the slots is very limited whatever type of end gland fitting I construct.